Be extraordinarily careful when replacing the rear view mirror on the XJ8, XK8 and XJ6 as the windshield can crack very easily. I did it (see below) but would recommend taking it to a windshield installer and have the old mirror removed and new one installed. The procedure is gut wrenching and nerve racking. Here goes:

Remove the upper and lower wire housing covers from the mirror. Caution: The upper cover has 2 very small plastic "pins" that break very easily.

Remove the interior head console. Open the sunglass visor, remove the plastic screw and the unit will come down. CAUTION: Do not pull untill you have removed the console wiring harness from its plug.

Unplug the large yellow connector for the mirror harness assembly.

IMPORTANT: While the mirror is still in place, lubricate however you can (spray oil) the area where the mirror slides onto the metal nut that is affixed to the windshield. Do not worry about getting oil on the glass = it's better than having the winshield crack.

CAREFULLY with even pressure and VERY LIGHT torque, "jiggle" the mirror to just slightly loosten it. ADD more oil. I'd call it even a "wiggle in place". Work the lubricant in/around before trying to "slide" the mirror down.

When you are satisfied (DO NOT jip yourself on time here guys and gals) that the windshield mounting nut is lubricated and the mirror mounting snap clip is lubed, GENTLY slide the mirror downward. Let the lube sit in place for a while. You may need to wiggle it a little through the motion.

GENTLY slide the mirror "upwards" using a very slight "wiggle" to get the snap ring to lock around the metal nut.

Reinstall the auto-wiper sensor harness, then plug in the mirror wire harness into the console area and reassemble the console.

Reinstall the plastic guards.

I've read about this proceedure online. One report indicated that professional techs break about 1 in 50 windshields doing this procedure. If you have good glass coverage with your insurance, go for it. If you don't, THINK TWICE about doing this even if your consider yourself an average to average plus mechanic. Glass has zero give.

If you need a new electochromatic mirror a good source is Jagbits - 888-524-2487. DO NOT buy a "used" mirror - Jag updated the faulty design in 2003 and the new mirrors are not supposed to fail.